Part of the TeachMe Series

Fitting an Intrauterine Device or Intrauterine System

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Original Author(s): Oliver Jones
Last updated: 20th December 2022
Revisions: 17

Original Author(s): Oliver Jones
Last updated: 20th December 2022
Revisions: 17

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The intrauterine device and intrauterine system are both long acting reversible contraceptives that are fitted inside the uterus:

  • Intrauterine device (IUD) – refers to the copper coil. It releases copper, which makes the uterus an unfavourable environment for sperm. The IUD is also thought to create an endometrial inflammatory reaction, inhibiting implantation if fertilisation has already occurred.
  • Intrauterine system (IUS) – refers to levonorgestrel-releasing coils, such as the Mirena® coil. It thins the endometrium (preventing implantation), and thickens cervical mucus (inhibiting sperm movement through the cervix).

These contraceptives are over 99% effective, but do not offer any protection against sexually transmitted infections.

In this article, we shall look at the procedure, indications and contraindications to fitting an intrauterine device or intrauterine system.


The IUD and IUS can be fitted at any point during the menstrual cycle:

  • Intrauterine device – provides contraception immediately after insertion.
  • Intrauterine system – only effective immediately if fitted within the first 7 days of the menstrual cycle.
    • If fitted at any other time, another form of contraception is advised for 1 week.

The procedure takes around 20 minutes to complete. A bimanual examination is performed (to assess for normal uterine anatomy), and a speculum inserted to visualise the cervix. A cervical dilator/sizer is passed through the cervix.

A small plastic T-shaped device is then pushed through the cervix into the uterus, where it remains. The strings attached to the IUD/IUS are cut so that they remain in the vagina. This allows the woman to check periodically to ensure the device has not been expelled.

Note: A sexually transmitted infection screen is usually performed two weeks before the device is fitted (recent exposure to an STI is an absolute contraindication). 

Fig 1 – Schematic of the copper coil within the uterus, and image of visible IUD strings on speculum examination.


The intrauterine device and intrauterine system are mainly indicated for use as a contraceptive. They are particularly suitable for women who often miss pills, or those who want long-lasting birth control.

Additional Indications

Intrauterine Device (Copper coil) Intrauterine System (Mirena®)
  • Can be used as emergency contraception, effective if fitted within 5 days of unprotected sex.


The absolute contraindications for the fitting of an IUS or IUD include:

  • Infection:
    • History of pelvic inflammatory disease
    • Recent exposure to a sexually transmitted infection
    • Recent infection of the uterus (e.g. septic abortion, post-partum endometritis).
  • Current pregnancy or up to 4-weeks post-partum
  • Uterine structural abnormalities (e.g. bicornuate uterus)
  • Current gynaecological malignancy
  • Current unexplained vaginal bleeding
  • Allergy to copper (IUD only)

In addition, the intrauterine system has the following contraindications (these are similar to the contraindications for other progesterone contraceptives):

  • Current DVT or PE
  • Current liver disease
  • History of breast cancer

Advantages and Disadvantages

It is important to fully counsel the woman about the advantages and disadvantages of the intrauterine device or intrauterine system:

Advantages Disadvantages
  • Very effective contraceptive.
  • Fertility usually returns to normal as soon as the IUD/IUS is removed.
  • Can be fitted at any stage of the cycle.
  • Can be used by women who are breastfeeding.
  • Can be used in (most) women for whom the COCP is contraindicated.
  • Mirena coil often produces lighter, less painful periods.
  • Copper coil is suitable for women who do not want to use hormonal contraception.
  • No protection against STIs.
  • Risk of ascending or iatrogenic infection.
  • Risk of uterine perforation at the time of fitting.
  • Risk of the body expelling the IUD/IUS.
  • The copper coil may make periods heavier and more painful.
  • There will most likely be an “adjustment period” after insertion of the coil which may consist of irregular bleeding for up to 6 months.
  • Insertion of the coil can be painful.
  • Although the risk of pregnancy is lower, there is a higher risk that any pregnancy will be ectopic.
  • Increased risk of seizures in epileptics at the time of cervical dilation.